A microfluid processing device comprises in general a microchannel, pumps, heaters, coolers and mixers such that a microfluid may be transported and processed inside and along the microchannel. Sometimes when the microfluid is in one section of the microchannel, at one terminal of the section is a heater and at the other terminal of the section is a cooler. Sometimes at one terminal of the section a reactant is added, while at the other terminal a different reactant is added. When a microfluid containing reactants is being processed in the microchannel uniform distributions of temperature and concentration are required. However, because of the large length to cross-sectional area ratio of microchannel it always happens that, when one terminal of a microfluid is being heated, the other terminal of the microfluid is being cooled at the same time. If this problem is not solved, a permanent spatial temperature gradient will exist in the microchannel, such that a uniform temperature distribution may not be obtained. In a microchannel, it also happens that, when a reactant is added into a section of the microfluid, the reactant can not travel to other sections effectively. Such a phenomenon makes it difficult to form a uniform distribution of reactants in the microfluid
In order to solve this problem, it is necessary to include a means in the microchannel, such that every part of the microfluid inside the microchannel may access the heaters or coolers directly and that reactants may be added into every part of the microfluid directly. As a result, an order-changing mechanism in the microchannel to change the spatial order of sections of a microfluid is required.